First isolation and characterisation of Encephalitozoon cuniculi from a free-ranging rat (Rattus norvegicus)     

Müller-Doblies UU  Herzog K  Tanner I  Mathis A  Deplazes P 《Veterinary parasitology》2002,107(4):279-285

The microsporidian species Encephalitozoon cuniculi can infect a wide variety of mammals including man. It is a common parasite in rabbits and several sporadic infections in laboratory rats have been described. Based on molecular data three E. cuniculi strains have been identified. Here we describe the first in vitro propagation of E. cuniculi, which was isolated from a free-ranging rat (Rattus norvegicus). The rat was one of three seropositive animals among 23 rats captured in the city of Zurich. The new isolate was further characterised as strain II ("mouse"-strain) based on the rDNA internal transcribed spacer sequence. Western blot analysis of this isolate revealed slight differences to other available strain II isolates originating from laboratory mice and farmed blue foxes. The new isolate caused disseminated infection in liver and lung upon oral inoculation of Brown Norway (BN) rats and was transmitted to sentinel rats. This rat-adapted isolate will be valuable to study the pathogenesis of Encephalitozoon infections in the rat model.  相似文献   

A proposal for isolating and testing phosphate-solubilizing bacteria that enhance plant growth   总被引：1，自引：0，他引：1  

Yoav Bashan  Alexander A. Kamnev  Luz E. de-Bashan 《Biology and Fertility of Soils》2013,49(1):1-2

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The effect of an NH4 +‐enhanced nitrogen source on the growth and yield of hydroponically grown maize (Zea mays L.)     

K. G. Alexander  M. H. Miller  E. G. Beauchamp 《Journal of plant nutrition》2013,36(1):31-44

Increased above‐ground dry matter and grain yields were found for two hydroponically grown maize hybrids (Pioneer‐3925 and Pioneer‐3949) when plants were supplied with an NH₄ ⁺‐enhanced nutrient solution (31 percent of total N) compared with a control (4 percent of total N as NH₄ ⁺). The major difference in yield developed between silking and 2 weeks post‐silking and silking and 4 weeks post‐silking for the P‐3925 and P‐3949 respectively. The reduced nitrogen content of the stover (leaves plus stalk) was consistently higher on the NH₄ ⁺‐enhanced nutrient solution. The decreased production of the control treatment may have resulted from a reduced photsynthetic capacity.  相似文献   

Silicon decreases the arsenic level in rice grain by limiting arsenite transport   总被引：1，自引：0，他引：1  

Alexander T. Fleck  Jürgen Mattusch  Manfred K. Schenk 《植物养料与土壤学杂志》2013,176(5):785-794

Silicon (Si) reduces arsenic (As) levels in rice shoot and grain. However, the underlying mechanisms remain unclear. In this study, we examined the effect of Si application to three rice paddy soils on the dynamics of Si, iron (Fe), phosphorus (P), and As in the soil solution, As accumulation in rice straw, flag leaf, husk, brown rice, and polished rice, and on As speciation in polished rice. Silicon application to soil increased the concentrations of Si, Fe, As, and P in the soil solution, while the redox potential was unaffected. Arsenic concentrations of straw, flag leaf, and husk were reduced by half by Si application, while As concentrations of brown and polished rice were decreased by 22%. The main As species in polished rice was arsenite, As(III), with a fraction of 70%, followed by dimethylarsinic acid (DMA) and arsenate, As(V), with 24% and 6%, respectively. Silicon application to the soil did not affect DMA or As(V) concentration of polished rice, while the As(III) concentration was reduced by 33%. These results confirm that Si reduces As(III) uptake and translocation into the shoot. Furthermore, data indicate that decrease of As concentration of polished rice is due to decreased As(III) transport into grain. Possible underlying mechanisms are discussed.  相似文献   

Evidence for the release of sex pheromones by male round gobies (Neogobius melanstomus)     

Barbara Zielinski  Wesley Arbuckle  Andrea Belanger  Lynda D. Corkum  Weiming Li  Alexander P. Scott 《Fish physiology and biochemistry》2003,28(1-4):237-239

We report supporting evidence for the hypothesis that nesting round goby parental males release sex pheromones to attract females, and the results of preliminary experiments into pheromone isolation. We assessed pheromonal communication through physiological (electro-olfactogram, EOG) and behavioral responses of females to water conditioned by males. Reproductive (R) females responded with larger amplitude EOGs to water conditioned by (R) males compared with non-reproductive (NR) males. The R females reacted by directed movement to water conditioned by R males compared to untreated water, but not to water from NR males or females. We are isolating odorous compounds from this conditioned water by fractionating non-aqueous components, and testing for olfactory (EOG) potency. The R females showed strong EOG responses to a subset of HPLC fractions collected from water conditioned by R males, but not to NR male fractions; and the R male fractions were not stimulatory to N females. We have initiated identification of the pheromonal source through in-vitro incubation of testicular cells with tritiated substrates. Seven metabolites were formed from androstenedione in the testis. One of these (albeit in a low proportion) was recognized as etiocholanolone. However, the HPLC elution position with maximal EOG activity did not with the elution position of this steroid (and all but one of the unidentified metabolites). This preliminary study suggests that the round goby may use a steroidal compound(s), or metabolite(s) for reproductive pheromonal communication.  相似文献   

Effect of varying dietary lipid and protein levels on growth and reproductive performance of female swordtails Xiphophorus helleri (Poeciliidae)     

Shirley Ling  Roshada Hashim  Sagiv Kolkovski  & Alexander Chong Shu-Chien 《Aquaculture Research》2006,37(13):1267-1275

We conducted a study to determine the effect of dietary protein and lipid levels on the growth and reproductive performance of a freshwater ornamental species, the swordtail (Xiphophorus helleri). Two protein levels (20% and 30%) with four lipid levels (8%, 12%, 16%, 20%) within each protein levels were tested through formulation of practical diets labelled as 20P8L, 20P12L, 20P16L, 20P20L, 30P8L, 30P12L, 30P16L and 30P20L respectively. Results showed that dietary protein level significantly influenced final weight, weight gain and specific growth rate, while dietary lipid did not influence any of these growth parameters. More specifically, increasing dietary lipid levels from 8% to 12–16% in both 20% and 30% protein levels significantly improved swordtail growth performance. Dietary protein levels positively influenced gonadosomatic and hepatosomatic indexes. Both dietary protein and lipid significantly influenced female muscle protein content. Significantly highest fry production was obtained from diets 30P12L and 30P16L, respectively, while diet 20P8L resulted in the lowest fry production. This present study indicates the dietary protein and lipid requirements for female swordtails for optimized growth and reproductive performances to be at 30% and 12% respectively.  相似文献   

Influence of dietary protein levels on growth and egg quality in broodstock female bagrid catfish (Mystus nemurus Cuv. & Val.)     

Muchlisin Zainal Abidin  Roshada Hashim  & Alexander Chong Shu Chien 《Aquaculture Research》2006,37(4):416-418

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Reactions of temperate reef fish larvae to boat sound     

Christian Alexander Jung  Stephen E. Swearer 《水产资源保护:海洋与淡水生态系统》2011,21(4):389-396

Effect of algal diet and temperature on the biochemical composition of the rotifer, Brachionus plicatilis     

Alexander P. Scott  Stephen M. Baynes 《Aquaculture (Amsterdam, Netherlands)》1978,14(3):247-260

Rotifers were fed on four species of unicellular algae (Dunaliella tertiolecta, Pavlova lutheri, Phaeodactylum tricornutum and Isochrysis galbana) at a range of temperatures. Measurements were made of growth rate, weight and level of total protein, carbohydrate and lipid. Large differences were found in rotifer weight and biochemical composition as a result of feeding and starvation. There were only minor differences attributable to the type of alga used as a food.  相似文献   

Using an age-structured model to simulate the recovery of the Australian pilchard (Sardinops sagax) population following epidemic mass mortality     

Alexander G. Murray  Daniel J. Gaughan 《Fisheries Research》2003,60(2-3):415-426

An age-structured model of the Australian pilchard’s population has been adapted to simulate recovery from the mass mortality suffered during the herpesvirus epidemics of 1995 and 1998/1999. The model generates a vigorous recovery even when levels of mortality are very high, which accords with observations. In spite of this strong recovery, the model indicates that stock is sensitive to increased fishing pressure. Healthy stocks of juvenile pilchards play a key role in the vigorous post-epidemic recovery.  相似文献